Control apparatus for automatic welding heads



July 25, 1950 F. c. KNIGHT EI'AL 2,516,777

CONTROL APPARATUS FOR AUTOMATIC WELDING HEADS Filed July 28, 1947 INVENTOR. FLOYD C. KAI/6H7 4N0 ELL/O7 C. COQNELL JP.

ATTORNEYS.

Patented July 25, 1950 CONTROL APPARATUS FOR AUTOMATIC WELDING HEADS Floyd 0. Knight and Elliott C. Cornell, Jr., East Cleveland, Ohio, assignors to The Auto Arc- Weld Manufacturing Company,

Cleveland,

Ohio, a corporation of Ohio Application July 28, 1947, Serial No. 764,090

This invention relates to welding heads for positioning and feeding a welding electrode, especially to welding heads that automaticall feed Weld rod to the Weld, dependent upon the rate of deposit of weld material.

Welding heads of the above class have heretofore been provided, as exemplified by the structuresshown in Patents 1,514,591, 1,514,592 and 1,563,612. The welding heads include two electric motors which connect through a dilferential to a shaft that controls the feed of the weld rod. The motors are driven in opposite directions with one motor'being adapted to drive the weld rod towards the weld and with the second motor being driven so as to' :lift. the weld rod away from the weld. The first of these motors is ordinarily controlled byv the current through or voltage on the weld while the second motor usually is a constant speed device.

The-previous types of. weldin heads and their controls have required both an A. C. and a D. C. energy supply, and some heads have been started and stopped by breaking the weld circuit which involves large, expensive circuit breakers, etc., as part of the control. Furthermore, some of these prior heads also have been bulky, have required use of involved starting circuits, have been diificult and. expensive to install, have had a large number of costly operating parts, or have been otherwise objectionable.

A general object of this invention is to avoid the foregoing and other disadvantages of the objectionsto prior types of automatic welding heads andto provide a welding head and control that is, characterized by its ability to function from a standard 110 volt 60 cycle supply.

. A further object of the invention is to provide a, small, compact, light weight automatic welding head which can be easily installed and which has a minimum of operating parts.

Another object of the invention is to position the electrode in predetermined relationship to the work prior to closing the welding or control circuits.

Yet another object is to provide a welding head control-with all of the control relays being contained in a control cabinet and with at least substantially all of such relays being directly connected to switches.

Another object of the invention is to provide a separate electrode control switch that will operate one control motor in either direction to bring it to a desired starting position.

Another object of the invention is to retain the weld circuit closed a short interval after the feedlaof the weld rod has been discontinued to prevent the formation of a crater at the end of :weld.

8 Claims. (Cl. 314-62) Further and more limited objects of the invention are to start both control motors simultaneously; to provide a D. C. motor in parallel with the weld circuit to control the feed of the weld rod towards the weld; to insert a high resistance automatically in the armature circuit of the D. C. motor when it is started; to reduce the resistance in the D. C. armature circuit after the motor is started; and to rectify part of the A. C. supply for use in setting up a D. C. field for the D. C. motor.

The foregoing and other objects and advantages of the invention will be made more apparent as the specification proceeds.

Reference is made to the accompanying drawing which is a diagrammatic showin of the electric circuit of the automatic weld head and control. of the invention.

An important feature of the invention is that power is provided for operating the automatic welding control, indicated generally by the numeral ill, by leads II and ii that connect to a standard suppl of 110 volt cycle current. The welding current, in this instance D. C., is provided by means connected to leads l3. and It with lead l3 connecting to the electrode or weld rod l5, and lead 14 connecting to the work W. The electrode I5 usually comprises a continuous Wire.

As in previous apparatus similar to that of this invention, two oppositely rotating motors, an A. C. motor l6 and a D. C. motor I1 are connected together through a differential I'll which connects to the motor shafts. The differential i8 is thus caused to rotate only through differences in speeds of the motors l6 and ll. The motor (6 is a constant speed motor while the motor I! is a variable speed motor adapted to alter its speed in accordance with the weld conditions. The differential l8 has a shaft l9 extending therefrom Which connects to a member 20 that is secured to the electrode I5 in any suitable manner so as to position such electrode with relation to the work and control the rate of feed of the electrode. The control means of the invention are connected to this substantially standard motor-differentialelectrode control so as to maintain the electrode 15 in desired relationship with the work W.

One special feature of the A. C. motor is is that it is a split-phase motor and has two fields by which it can be operated. One field, the run field -'2l is connected to leads 22 and 23, while the second or start field 24 connects to leads E5 and 26. Reversal of the start field of the motor I6 is adapted to cause it to rotate in opposite directions with the run field being normally adapted to drive shaft 21 secured to the motor It in such a direction as to cause the differential I8 and means 20 to raise the electrode [5 with relation to the work. Shaft 28 connects to the motor I1 and in turn connects to the diiferential I8 so as to cause means 26 to move the electrode l towards the work whereby these motors, by variation of their relative speeds, can maintain the electrode in desired relationship to the work after a weld has been started by controlling the feed of the electrode wire I5.

In order to set the electrode l5 in a predetermined relationship to the work W prior to starting weld action, a three-connection, two closed position switch 29 is provided. This control switch 29 has contact members 3!, 32, and 33, and 3|a, 32a and 33a with the contact members 3|, 3|a, 32 and 32a being connected together by lead 34 which, in turn connects to lead 36 that extends from the power supply lead l2. The remaining contact members Y33 and 33a connect to a lead 35. which in turn connects to lead 36 that extends to the opposite power supply lead so that a circuit can be set up through the switch 28. Contact points 31, and 38; 39 and 48; and 4| and 42 are provided in the switch 29 for as sociation with the contact members 3|, 3m, 32. 32a, 33 and. 33a respectively. Switch 29 also has a connecting lead 43 extending between contacts 31 and 38 while leads 44 and 45 extend between the diagonally opposed contacts 39 and 42, and 46 and 4|, respectively. The switch is adapted to .close either contact members 32 and 33, or 32a and 33a, as desired. Hence by moving the control bar 46, associated with the three contact members and to whichsuch members are se- ;An A. C. interlock relay 53 is provided between the control switch 29 and the motor. l6 for regulating the operation of such motor. This relay 53 has an operating coil 54 and it includes two pairs of switches or contacts 55, 55, and 56,56. One of each of the contacts 55, and 56 is positioned in leads 51 and 58 which extend through the relay and connect to contacts 4| and 42 of 1 Leads 22 and23 conthecontrol switch 29. v nect to the leads 51 and 58 intermediate the switches or contacts 55 and 56 and such leads 22 and 23 connect to the field 2| of motor l6 for energizing that field. Normally the contacts 55 are closed whereby current will flow to the field 2| as soon as either set of contacts of the switch 29, 32 and 33, or 32a and 33a is brought into engagement with its associated contacts. Energization of the field 24 of motor I6 is effected by both closed positions of switch 29 and the reversal of the motor I6 is achieved by changing the power supply connections of the field 2|, dependent upon the position of the control switch 29. That is, the control bar 46 can be moved to close contact arm 32a against contact 40 so lead 45. lead 51 and lead 22 energize one side of the field 2| while its other side connects through lead 23, 58, contact 42, contact arm 33a andlead to the opposite power lead. Or, the control bar 46 can be moved to close contact arm 32 against contact 39 and contact arm 33 againstcontact 4| which reverses the flow of current through the run field 2|. In either closed position of switch 26, arm 3| or 3la--closes a circuit, from power lead l2 through leads 3!! and 34, contact 31 and lead 43 or contact 38, to a lead143a that extends to lead 26 for the field 24. other side of field 24 connects to power lead by contact 48 connects to the lead 26 of the start 4 through lead 25 and a lead 69. Hence the switch 29 provides means for rotating the motor l5 in either-direction when the remainder of the apparatus is not functioning;

A starting switch 41 is provided for the apparatus l8 and such switch 41 includes three contact members 48, 49 and 58 with contacts 48 and 49 being connected to lead 36 and being adapted to close circuits to leads 5| and 52 respectively.

From the starting switch 41, the lead 5|, closed field 24 of the motor l6 and causes the motor Hi to start and run in such direction as to feed the electrode I5 away from the work W. The

second contact arm of the start switch 41, through lead 52, connects to a conventional rectifier unit 6|, such as a selenium rectifier, which is adapted for full wave rectification of the A. C. energy supplied thereto. Lead 36 extends to the rectifier unit 6| to complete the circuit therefrom for its energization. A variable resistor 62 is provided in lead 52 so as to provide a control for the voltage output of the rectifier unit 6 Leads 65 and 66 connect the output side of the rectifier 6| to a separately excited field 61 for the motor |1 whereby a constant D. C. voltage is supplied for such field and control of the motor I1 is effected by variation of its armature current; as hereinafter explained. However, the motor l1 can also be controlled by variation of the resistance 62,

1 when desired. A lead 68 ,extendsfrom'the lead 52 of the switch 41 to, the lead 58 and extends to the operating coil 54 for relay 53 a circuit throughwhich is completed to power supply lead I by lead 66. Hence the relay 53 is energized when the switch 41 is closed. Energization of the relay 53 causes it to open contacts 55, 55 and close contacts 56, 56 whereby the preset switch 29 is cut out of the control circuit and the fields 2| and 24 of motor |6 are so correlated as to cause the motor to drive the motor to raise the electrode |5'from the work.

So as to control the weld circuit, a lead 10 connects to the lead 68 and connects it to the power supply lead through operating coil 1| of a delay relay 12. This delay relay 12 controls a switch or contact element 13 which is included in thelead l2 and controls theflow of current through an operating coil 14 of a relay 15 which controls contacts 16 in the weld circuit. Thus closing switch 41, through the contact element 49 thereof, also energizes the delay relay 12 which, in turn, energizes coil 14 of relay 15 so as to close contact 16 and complete the weld circuit for weld action. The contacts 13 have a delay element, such as a dash-pot 11, connected'to themor their controls whereby the contacts 13 are not immediately opened when the coil 1| is de-energized, but a slight'and variable time lag is effected before the contacts 13 are opened whereby operating coil 14 of the weld control relay 15 is temporarily energized after the start or control switch '41 is opened. Hence current flows through the weld circuit for a slight'interval after the control circuit for the apparatus Ill is opened and this prevents formation of a crater in the weld at its terminal end.

In order to control the current flowing through the armature of motor IT on closing the switch has an operatingcoil 19 which is connected in series with the motor armature whereas asecond. operating coil is connected in parallel'with" aura???- such armature. Such coils 'ls arid-80 each control one position or setting of the relay which hastwo operative positons sothat the coils l9 and-8U are, ineffect, opposed and one must overcome the other tochange the setting of the relay. The parallel-coil 80 is directly connected between the leads [3 and M of the weld circuit so that such coil is energized immediately and suifioiently upon closing the contact 16 by the high inrush current so that it controls the relay setting. This coil 80 then serves to hold in the relay 18 until balanced circuit conditions and normal weld voltage are established. The armature of motor I! connects to the switch element 50 of the starting'switch 4'! by a lead 8| whereas a lead 82 connects the other side of such switch element 50 back through the operating coil 18 to the weld current supply lead l4. Lead I08 connects the armature of motor H to weld circuit lead [3. The relay I8 is adapted, when high open circuit voltage is impressed on the motor armature circuit, to open a pair of contacts 83 and 84 which normally are held in electrical contact with a contact 85 by a variable tension spring l8 so that a variable resistance 88, connected to the contacts 83 and 84, is placed in the armature circuit for motor II. This resistance 86 is of sufiiciently high value as to reduce the armature current appreciably on starting so as to slow down the armature speed and hence downward movement of the electrode IE to a desired value. The apparatus of the invention normally has a separate generator associated with it for provision of weld current and its open circuit terminal voltage is appreciably higher than its terminal voltage when weld current is passing therethrough. When normal welding voltages exist on the armature of the motor l1, after a weld arc is struck, the relay 78 is adapted to close contacts 83 and 84 against contact 85 and short out the resistance 86, as the coil 88 will no longer be energized sufficiently to hold the relay with contact 85 open. The series coil 19 is provided to aid in snapping the relay 18 to its run position wherein a secondary adjustable resistance 81 is connected in the circuit. On normal operating conditions, the relay 18 holds open contacts 88 and 89 that connect to the resistance 81 and they insert such resistance in lead 82 of the armature circuit with spring l8 urging contact 90 to its open position. However, when high starting voltages exist, the resistance 81 is shorted out of the circuit by the relay (8 through the contact 90 which is associated with the'contacts 88 and 89 since at such time, the coil 80 is sufliciently energized to overcome the action of the spring urging contact 90 toward its open position. Hencemeans are provided for automatically limiting the initial current through the armature of motor I! and such means automatically adjust the resistance in the armature circuit to permit it to feed the electrode down towards the work, in combination with the motor l6 and its action, at the desired rate. The resistance 86 is adjusted when the control apparatus is initially coupled to its welding circuit, but once adjusted, usually requires no further variation forgiven weld conditions. Then, after adjusting the resistor 82, the apparatus I0 is ready for complete automaticaction after these few simple adjustments are made. Since the control apparatus can be plugged into an ordinary 110 volt 60 cycle power supply, it is very easy to set up, or install. The weld leads l3 and ll, of course, also can easily be connected to leads 82 and I00 of the armature circuit oi. motor I! to connect the motor:.--in parallel to-the Weld and have'the speed of the motor vary in accordance with the weld resistance.

Also, in some instances, itmay be-desirab1e to connect the relay 75 to other than the weld circuit so as to permit the useof lighter circuit breakers. Hence, we may connect the relay 15 so that it controls the field circuit of thegenerator connected to the apparatusfor supplyof welding current.

Should the control apparatus Ill be used with an A. C. weld circuit, conventional means, such as a transformer and a rectifier should be-con-- the arma-- nected between the weld circuit and ture of the D. C. motor. I

In order to slow down the motor l6 and permit fine control on the starting positonof the electrode I5, a resistance 34 is connected in the lead 34 to reduce the speed for inching the electrode into a desired position. Theresistance 3-1 may be variable, if desired.

One completeembodiment of theinvention has been illustratedand described indetail herein but? it will be realized that the invention is not limited to the specific example set forth since modification may be resorted to within the scope of the appended claims;

We claim:

1. An automatic .weld head controliorsupplyr variable speed D. C. motor connected to said:

differential means for. driving it, said. D; C'. motor having its armature connected in par allel to the arc, rectifier means having a constant D. C. output, means for connecting said rectifier means to an A. C. power supply, means for connecting the D. C. output of said rectifier means to the separately excited field of said D. C. motor, said A. C. motor having two fields the reversal of one of which will cause opposite rotation of the motor, a separate starting and reversal switch for said A. C. motor, a relay connected in the circuit between said switch andsaid motor and being adapted to open such circuit when energized, and a common starting switch for both of said motors, said common starting switch being connected to a conventional A, C. power supply and to said relay for energizing it when such switch is closed for cutting said separate starting and reversal switch out of the circuit.

2. In an-automatic welding head control for supplying current to an are through an electrode for a weld, a D. C. motor having a separately excited field, the armature of. said motor being connected in parallel to the arc, a relay having an operating coil connected in series with said motor and having a second operating coil connected in parallel to the arc, said parallel operating coil being adapted to hold in said relay until a weld arc is struck, and a high and a low resistance connected to said relay which is adapted to change the armature circuit to insert.

said high resistance in the armature circuit when starting said motor, said relay changing its' position to remove said high resistance from the armature circuit substantially simultaneously with the establishment of a Weld arc, a low resistance being included in the armature circuit after the weld arc is struck.

3. In an automaticwelding head control for supplying a current to an are through an electrode for a weld, a D. C. motor having a sepa-.

rately excited field, the armature of said motor being connected in parallel to the arc, a relay.

havin an operating coil connected in series with the armature of said motor and having a second operating coil connected in parallel to the am, said parallel operating coil being connected to the power supply of the weld circuit and being adapted to place and hold said relay in a given position until aweld .arc is struck, and resist-.

ance means connected in the armature circuit of said. motor withthe value of same being controlled by the setting of said relay, said resistance meanshaving. a high anda low. resistance, said relay inserting the highresistance .in'the armature. circuit before a weld arc is established and cha ging the relay position to insert the low resistance. inthe armature circuit after the weld connected in circuit with saidmotor, said relay.

having an operating coil. connected in parallel with the weldcircuit and an operating coil.con-.

nected in series with said armaturecircuit, and

a high and a low resistance associated with said armature circuit and said relay, said relay having two operative positions. with one position being controlledby said parallelcoil andbeing adapted. to insert said high resistance in said armature circuit, the other position of said relaybeing controlled by said. series. coil and being adapted to insert said low resistance in series...v with said armature circuit, said relay ,being con structed and arranged so that said parallel coil controls said elay Whentheweld circuit isopen and said series coil controls .it when said weld circuit is closed. 1

5. In an automatic tus for supplying current to an are through an electrode, an electric motor, an A C. motor having two fields the'reversal of one of which will cause opposite rotation of the motor, a separate starting and reverse switch for said A. C. motor,' a relay .connectedin the circuitfbetween said switch and said motor and being adapted 'to oper'i' such circuit when energized, and a common start-" ing switch for both of said motors, said common starting switch being connected to a power supply and to said relay for energizing it when such switch is closed for cutting said separate starting and'reversal switch out of the circuit of said A. C.

motor. 1

6. In an automatic weld head control appara-* tus for supplying current to an are through an electrode, a constant speedA. C. motor, a variable speed D. C. motor, said D. C. motor having its armature connected in parallel to an are controlled by the apparatus, rectifier means having a con-- stant D. C. output, means for connecting said rectifier means to an 'A..C. power supply, means for connecting the D. C. output of said rectifier means to the field of said D. C. motor, said A. C.

motor having. twofields the reversal of one ofweld head control appara 8. which will cause opposite rotation ofthe motor, a separate starting and reversalswitch for said A. C. motor, a relay connected in the circuit be tween said switch and said motor and being adaptedto open such circuit when energized, and a commonstarting switch for both of said motors,

saidcommon starting switch being connected to a 1 conventional A. C. power supply and to said relay for energizing .it'when such switch is closed for cutting said separate starting and reversal switch out of the circuit.

7. In an automatic welding headcontrol for a circuit having a. greater open or starting circuit voltage than Weld circuit voltage, a D. C. motor having its armature connected in parallel to the weld, said motor having a separately excited field, a relay having an operating coil connected in series with the armature of said motor and a second operating coil connected in parallel to the weld, said relay havinga starting and a running position, said second operating coil being constructed and arranged to hold said relay in a starting position on the high circuit voltage existing until a weld arc is struck, and a resistance con-trolled by said relayand connected in its starting position in the armature circuit of said motor, said first operating coil overcoming the action of said second coil when normal weld circuit voltages are impressed on saidrelay to set same at its running condition to cut out said resistance from said armature circuit.

8. In an automatic welding head control in a welding circuit having a greater starting circuit voltage than the weld circuit voltage, a D. C. motor having a separately excited field, the armature of said motor being connected in parallel to theweld produced in the circuit, a relay having an operating coil connected inseries with the armature of said motor and a second operating coil connected in parallel to. the weld, said relay having a starting'and a running position, said second operating coil being constructed and arranged to h'oldsaid relay in a starting position on the high starting circuit voltage existing until a weld arc is struck, and a resistance circuit controlled by said rela'y and connected in its starting position in the armaturecircuit of said motor, said first operatingcoil overcoming said second coil when operating conditions exist and setting said relay in its running condition to cut out said resistance circuit from said armature circuit.

' FLOYD C. KNIGHT.

ELLIOTT C. CORNELL, JR.

REFERENCES CITED JThe following references are of record in the file of thispatentz' M 'UNITED STATES. PATENTS Nyburs Apr. 26,1949 

